JPH0751241B2 - Method for producing stainless cold-rolled steel strip - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a cold rolled stainless steel strip having excellent surface gloss.

[Prior Art] Conventionally, a stainless steel cold-rolled steel strip has a large amount of rolling oil such as a Sendzimir mill that uses a work roll having a small diameter of 150 mmφ or less, while the surface of the hot-rolled steel strip subjected to intermediate annealing and pickling While cold-rolling (hereinafter abbreviated as cold-rolling) while supplying the product, and then finish annealing pickling or finish bright annealing, and then finish temper rolling with a rolling reduction of 0.5 to 1.2%. Was there.

Further, in recent years, as a method for highly efficiently manufacturing a stainless cold-rolled steel strip by greatly shortening the rolling time, a manufacturing method using a cold tandem mill equipped with a work roll having a large diameter exceeding 150 mmφ has been adopted. .

The stainless cold-rolled steel strip manufactured through these steps is often used as it is on the surface after production, for example, in the case of a ferrite system typified by SUS430, and is excellent in the product after the above-mentioned finish temper rolling. Surface gloss is required. Also, SUS304
In the case of the austenite type represented by, the products whose surface gloss is imparted by buffing after finish temper rolling are often used, and it is important to exhibit excellent surface gloss after this buffing.

[Problems to be Solved by the Invention] Conventionally, in order to obtain an excellent surface gloss for both ferrite type and austenite type in cold rolling using a small diameter work roll such as Sendzimir mill, for example, Japanese Patent Publication No.
As described in Japanese Patent Publication No. 57-13362, the average roughness Ra is 0.2 to 1 μm in the pass before the finishing pass, and the average roughness Ra in the finishing pass.
A method of using a work roll of 0.1 μm or less is adopted. However, when this method is used, the surface roughness of the work roll in the pass before the finishing pass is large and the roughness remains on the plate surface after cold rolling, so that the surface gloss is not sufficiently satisfactory. .

Further, when cold-rolled by a tandem mill equipped with a large-diameter work roll, the roughness of the steel strip surface before cold rolling, that is, after intermediate annealing pickling is significantly large, and the roughness is cold-rolled. After that, the work roll surface roughness during cold rolling is large, and the roughness also remains on the surface of the steel strip after cold rolling.As a result, the gloss of the steel strip surface after production is significantly inferior. Was there. Therefore, as a method for solving this kind of surface gloss reduction problem, there is a conventional method, for example, Japanese Patent Laid-Open No. 61-49701.
A method for devising a combination of roll roughness and work roll diameter as described in Japanese Patent Publication is disclosed. This is a method for preventing plate surface flaws called gold dust, which has a purpose different from that of the present application for improving the surface gloss itself. However, when this method is adopted, the above Japanese Patent Publication No. 57-13362 is used. Similar to that of the publication, a significantly large roughness of the steel strip surface after annealing and pickling the hot rolled steel strip remains after cold rolling, the surface gloss of the product is insufficient, and
It was recognized that improvement was needed.

The present invention is a rolling using a small diameter work roll such as a Sendzimir mill, a rolling using a large diameter work roll such as a cold tandem mill and a cold rolling combining these,
The purpose of the present invention is to solve the conventional problem of lowering the surface gloss and to produce a stainless steel strip of excellent quality.

[Means for Solving the Problems] The present invention according to claim 1 is a method for manufacturing a stainless cold-rolled steel strip by rolling using a large-diameter work roll. The pre-treatment of non-lubricating rolling is performed under a rolling reduction of more than 5%, and then, during cold rolling, before the final stand before the final stand, the stand before the final stand or the final stand. Cold rolling is performed while supplying the rolling oil using a work roll having an average roughness (Ra) of 0.2 μm or less in a plurality of continuous stands including the one in front. While supplying the average roughness (Ra) 0.15μ
Cold rolling is performed using a work roll having a roughness of m or less.

The present invention according to claim 2 is a method for manufacturing a stainless cold-rolled steel strip by rolling using a small-diameter work roll, wherein after annealing and pickling the stainless hot-rolled steel strip, it is further subjected to a rolling reduction of more than 5%. A pretreatment of non-lubricating rolling is performed, and thereafter, at the time of cold rolling, before the final preceding pass, a final preceding pass, or a plurality of final preceding passes. Average roughness (Ra) 0.2 μm in successive passes
Using the work rolls with the following roughness, cold rolling is performed while supplying the rolling oil, and while the rolling oil is also supplied in the final pass, the work rolls with the average roughness (Ra) of 0.15 μm or less are used. It is used for cold rolling.

The present invention according to claim 3 is a method of manufacturing a stainless cold-rolled steel strip by rolling using a large-diameter work roll, followed by rolling using a small-diameter work roll. A pre-treatment of non-lubricating rolling is performed under a rolling reduction of more than%, and then, during the cold rolling, before the final preceding pass, the final preceding pass, or the final pass. Cold rolling is performed while supplying the rolling oil using a work roll with an average roughness (Ra) of 0.2 μm or less in multiple consecutive passes including the preceding pass, and the rolling oil is also fed in the final pass. While being supplied, cold rolling is performed using a work roll having an average roughness (Ra) of 0.15 μm or less.

[Operation] Generally, in order to improve the surface gloss of a stainless cold-rolled steel strip, it is necessary to reduce the surface roughness of the finished product, and the surface roughness of this product is the steel after cold rolling. It is known that the surface roughness of a finished product is significantly influenced by the surface roughness of the strip, and whether the surface roughness of the finished product is good or bad depends on the surface roughness after cold rolling. Therefore, conventionally, as described above, a method has been adopted in which the surface roughness of the steel strip is lowered during or after cold rolling in which a large amount of rolling oil is supplied.
Hereinafter, cold rolling in which a large amount of rolling oil is supplied is simply referred to as cold rolling.

However, according to the study of the present inventors, the surface roughness of the steel strip after the cold rolling is the steel strip before the cold rolling, that is,
Remarkably large surface roughness of steel strip after annealing and pickling remains after rolling, work roll roughness during cold rolling transferred to steel strip, and oil pits generated during cold rolling It was clarified that there are three of them.

Then, first, the residual of the surface roughness of the steel strip after the pickling of the hot rolled steel sheet by annealing will be described.

In the production of stainless cold-rolled steel strips whose target finish is an average roughness Ra of 0.1 μm or less, the surface roughness immediately after annealing and pickling of hot-rolled steel sheet is such as shot blasting during pickling. By mechanical descaling and acids such as sulfuric acid,
The average roughness Ra2 to 4 μm is extremely large.

By the way, during cold rolling, rolling oil is supplied to the steel strip surface and the roll surface. Therefore, the rolling oil adheres to the surface of the steel strip on the entry side of the cold rolling, and the oil is collected in the recess having the above-mentioned extremely large surface roughness and bites into the roll bite. The oil accumulated in the recess is rolled in the roll bite while the roll and the steel strip are in contact with each other, while there is no escape place and the oil is contained. In general, liquids including rolling oil are significantly less likely to be compressed than gases such as air,
The pits that contain oil during rolling are somewhat smaller than they were before rolling, but most remain after rolling. In this way, the surface roughness of the steel strip before cold rolling remains even after cold rolling, and the surface gloss of the product is significantly impaired.

That is, in order to obtain a steel strip having excellent surface gloss, it is better to reduce the unevenness of the steel strip surface before cold rolling in advance,
It is advantageous to make the surface of the steel strip smooth by rolling, but in the conventional cold rolling in which a large amount of rolling oil was supplied,
As described above, most of the irregularities on the surface of the steel strip before cold rolling cannot be eliminated.

In view of the above, in the method according to the present invention, first, as pretreatment before cold rolling, from the above-mentioned knowledge, non-lubricating rolling in which a liquid such as rolling oil is not supplied is performed before cold rolling under a rolling reduction of more than 5%. It is applied to a steel strip.

Here, the reason why the rolling reduction of more than 5% is required in the non-lubricated rolling is as follows.

In the study by the present inventors, at the time of non-lubricating rolling before cold rolling, hot rolling was performed by changing the reduction ratio in various ways, and then the steel strip annealed and pickled was rolled, and then cold rolled by supplying a large amount of rolling oil. The surface gloss of the stainless cold-rolled steel strip finished by hot rolling, finish annealing pickling or finish bright annealing, and finish temper rolling was investigated. As a result, the work roll diameter is 150 m
Rolling using a small diameter work roll such as mφ or less Sendzimir mill, rolling using a large diameter work roll such as a cold tandem mill that exceeds a work roll diameter of 150 mmφ, and in any case of cold rolling combining these. When the rolling reduction during non-lubricating rolling before cold rolling is increased, the surface gloss is hardly improved when the rolling reduction is 5% or less.
It has been found that when it exceeds%, it becomes extremely good.

Next, when the stainless steel strip after performing the non-lubricating rolling as described above is cold-rolled by supplying a large amount of rolling oil, depending on the size of the surface roughness of the work roll used at the time of rolling, it may be finished after rolling. A new problem arose that the surface gloss of the product was reduced.

That is, when the stainless steel strip after the non-lubricating rolling is cold-rolled, first, a large amount of surface defects called oil pits are generated during the cold rolling, so that the surface gloss of the finished product after the cold rolling is increased. Lower. It should be noted that, because oil pits have different easiness of deformation for each crystal grain on the surface of the steel strip, unevenness occurs for each crystal grain, and at the same time, an intragranular slip line of the crystal grain remains on the surface of the steel strip. And involves a very thin layer of rolling oil contained between the work rolls and the strip during rolling.

Further, if the work roll roughness is large, the size of the scratches transferred to the steel strip becomes large, and the surface gloss of the finished product after cold rolling is reduced.

Therefore, the present inventors have examined methods for avoiding a decrease in surface gloss due to these defects of oil pits and scratches, and have clarified that the following two methods are effective respectively.

As a first method, the present inventors use the average roughness of the work roll roughness in a final pass using a small diameter work roll of cold rolling or a final stand using a large diameter work roll.
It has been found that the surface gloss becomes good when Ra is 0.15 μm or less.

That is, the pass or stand that most affects the surface roughness of the steel strip after cold rolling is the final pass using the cold rolling small diameter work roll or the final stand using the large diameter work roll. Moreover, in cold rolling of ordinary steel, the transfer rate of roll roughness to the surface of the steel strip is 70-80%, whereas in cold rolling of stainless steel, the transfer rate is 90%.
Remarkably efficient as above. Therefore, if the roughness of the work roll is made small, the scratches transferred to the surface of the steel strip can be made small, and the scratches can be efficiently made small. Further, by reducing the work roll roughness, the rolling oil supplied at the final pass using the small diameter work roll or the final stand using the large diameter work roll is enclosed in the recess of the roughness and is a very thin oil. Although it is easy to form oil pits by forming a layer of No. 3, it was found that by reducing the work roll roughness, the recesses in the roughness are reduced and the oil that is enclosed is reduced, and as a result, the oil pits can be suppressed. is there. here,
If the work roll roughness of the final pass using a small diameter work roll or the final stand using a large diameter work roll exceeds the average roughness Ra of 0.15 μm, oil pits will frequently occur and large scratches will remain in large quantities, so after cold rolling. The finished stainless cold-rolled steel strip has a reduced surface gloss, so 0.15
It is necessary to limit the thickness to less than μm, but preferably 0.1 μm
When the amount is below, the surface gloss is further improved.

Next, the present inventors examined a second method for further improving the surface gloss over the first method, and found that the following method should be added to the above method.

That is, in addition to the above-mentioned method, at least the final one before the final pass using the small diameter work roll or the final one previous stand using the large diameter work roll, the final one using the small diameter work roll. Last pass using the previous pass or large diameter work roll, or a plurality of continuous passes including the last one previous pass using the small diameter work roll, or the last one using the large diameter work roll It is a method of cold rolling using a work roll having an average roughness Ra of 0.2 μm or less in a plurality of continuous stands including the front stand.

As mentioned above, the transfer rate of the work roll roughness of the final pass using the small diameter work roll or the final stand using the large diameter work roll to the steel strip surface is 90% or more, but the remaining 10% or less. Is a large work roll roughness of a pass or a stand before a final pass using a small-diameter work roll or a final stand using a large-diameter work roll, that is, a large scratch is transferred and left on the steel strip. Therefore, when rolling was performed by changing the average roughness Ra of the work roll before the final one pass using the small-diameter work roll or before the final stand using the large-diameter work roll, the surface gloss was further improved. It has been found that the average roughness Ra of those work rolls needs to be 0.2 μm or less in order to be good.

Further, similarly to the above, by reducing the work roll roughness of the intermediate pass using the small diameter work roll or the intermediate stand using the large diameter work roll, the roughness of the work roll and the steel strip surface at the entrance side of each pass or stand is reduced. It has been found that the oil enclosed in the pit can be reduced and the oil pit can be similarly suppressed by setting the work roll roughness to an average roughness Ra of less than 0.2 μm.

In order to reduce the work roll roughness to a predetermined value or less, each of the above methods is carried out by performing unlubricated rolling in excess of 5% before cold rolling according to the present invention, and after annealing pickling the hot rolled steel strip. When the method is applied to the conventional method of performing cold rolling in which a large amount of rolling oil is supplied after annealing and pickling, the effect is remarkably small.

[Examples] Tables 1 to 3 below, using a SUS430 steel strip as an example of a ferrite series and a SUS304 steel strip as an example of an austenite series, which were subjected to annealing pickling after hot rolling according to the method of the present invention.
Non-lubricating rolling was carried out at the reduction ratio shown in the table as an example, and then
The work rolls having the roughness shown in the table as an example were combined and cold-rolled, followed by finish annealing pickling or finish bright annealing, and finish temper rolling. At this time, the steel strip that had been subjected to finish annealing pickling of SUS304 was subjected to finish temper rolling and then subjected to buff polishing under the same conditions.

Further, as a comparative example of the present invention, after performing the non-lubricating rolling of the present invention, after cold rolling by combining the work rolls of the conventional roughness, finish annealing pickling or finish bright annealing,
Each was subjected to finish temper rolling. In the case of finish annealing pickling of SUS304, buffing was further performed under the same conditions as above.

In addition, Table 1 is for cold rolling using a large diameter work roll by a cold tandem mill, Table 2 is for cold rolling using a small diameter work roll for a Sendzimir mill, and Table 3 is a cold tandem mill. It shows the case of cold rolling with a Sendzimir mill after rolling.

Regarding the surface gloss of these stainless cold-rolled steel strips, the results of visual judgment are also shown in Tables 1 to 3.

In addition, the results of visual determination of the surface gloss of the stainless cold-rolled steel strip obtained by the conventional manufacturing method are also shown. The visual judgment was made into 5 grades of special A and A to D in the order of good gloss. In addition, when these five grades of visual judgment, special A and A to D, were measured by JIS Z 8741 glossiness measuring method 5 (GS20 °), special A was found to be 950 or higher, A to 800 to 950 was A, and 600 to 800 was It was found that B, 400 to 600 correspond to C, and 400 or less corresponds to D.

In the case of both ferrite type SUS430 and austenitic type SUS304, rolling using small diameter work rolls such as Sendzimir mill shown in Tables 1 to 3, rolling using large diameter work rolls such as cold tandem mill, and rolling combining these In, in the case of the stainless cold-rolled steel strip produced by the method of the present invention, it has a remarkably good surface gloss as compared with the steel strip produced by the conventional method, and the method of the present invention is remarkably effective in improving the surface gloss. Is clear.

In particular, the product subjected to finish annealing pickling of SUS304 gives surface gloss by buffing etc. after that, but when the method of the present invention is applied, the surface gloss after buffing is also higher than that of the steel strip produced by the conventional method. It has improved significantly.

[Effects of the Invention] As described above, the stainless cold-rolled steel strip manufactured by the method of the present invention is
It has a remarkably excellent surface gloss. In particular, when it is rolled by a conventional cold tandem rolling mill, the surface gloss is extremely inferior, and it cannot be applied at all in applications requiring gloss,
The product market was also extremely narrow. Moreover, the surface gloss of the Sendzimir rolled product could not be reached at all even by using various methods. However, according to the method of the present invention, it becomes possible to impart an excellent surface gloss equal to or higher than the surface gloss of a Sendzimir rolled product which has hitherto been unattainable. In addition, the method of the present invention performs unlubricated rolling exceeding a rolling reduction of 5%, which has never been known, and
This is a method carried out based on a new finding that oil pits are suppressed by reducing work roll roughness, and a combination of these methods has the effect of significantly improving the surface gloss.

Front Page Continuation (72) Inventor Akihiko Fukuhara 1 Kawasaki-cho, Chiba-shi, Chiba Inside Kawasaki Steel Co., Ltd. (72) Inventor Tomio Komatsu 1 Kawasaki-cho, Chiba-shi Chiba Steel Co., Ltd. (72 ) Inventor Akira Kishida 1 Kawasaki-cho, Chiba-shi, Chiba Inside the Chiba Works, Kawasaki Steel Co., Ltd. (72) Inventor Akira Kawarada 1 Kawasaki-cho, Chiba-shi, Chiba Inside the Chiba Works, Ltd. 1 Kawasaki-machi, Chiba-shi, Japan Inside Kawasaki Steel Co., Ltd. Chiba Works

Claims (3)

[Claims] 1. A method for producing a stainless cold-rolled steel strip by rolling using a large-diameter work roll, which comprises subjecting a hot-rolled stainless steel strip to annealing and pickling, and then performing non-lubricating rolling under a rolling reduction of more than 5%. Pretreatment, and then, during cold rolling, before the final one before the final stand, the final previous stand or an average of a plurality of consecutive stands including the final previous stand. Roughness (Ra) 0.
Using a work roll with a roughness of 2 μm or less, cold rolling is performed while supplying rolling oil, and while the rolling oil is also supplied to the final stand, a work roll with a roughness of 0.15 μm or less in average roughness (Ra). A method for manufacturing a stainless cold-rolled steel strip, which comprises performing cold rolling by using. 2. A method for producing a stainless cold-rolled steel strip by rolling using a work roll having a small diameter, wherein a hot-rolled stainless steel strip is annealed and pickled, and then a non-lubricated rolling preliminary is performed under a rolling reduction of more than 5%. After the treatment, during cold rolling, before the final one before the final pass, the final previous pass, or an average coarseness in a plurality of consecutive passes including the final previous pass. Using a work roll having a roughness (Ra) of 0.2 μm or less, cold rolling is performed while supplying the rolling oil, and the rolling oil is also supplied in the final pass, while the average roughness (Ra) is 0.15 μm or less. A method of manufacturing a stainless cold-rolled steel strip, comprising cold rolling using a work roll having a roughness. 3. A method for producing a stainless cold-rolled steel strip by rolling using a large-diameter work roll, followed by rolling using a small-diameter work roll, further comprising a rolling reduction of more than 5% after annealing and pickling the hot-rolled stainless steel strip. Non-lubricating rolling pretreatment under cold rolling, and then, before cold rolling, before the last one pass, before the last one pass or the last one pass. Using multiple work rolls with an average roughness (Ra) of 0.2 μm or less in multiple consecutive passes, cold rolling is performed while supplying the rolling oil, and the average is also applied while supplying the rolling oil in the final pass. A method for producing a stainless cold-rolled steel strip, which comprises performing cold rolling using a work roll having a roughness (Ra) of 0.15 μm or less.